The present invention relates to a relay connector for not exclusively but preferably providing a connection between flat cables.
Conventionally, relay connectors provide electrical connection between flat cables, each having flexibility and being often referred to as a flexible printed circuit (FPC) or a flexible flat cable (FFC). One such connector is described in Japanese Patent Application Laid-open (kokai) No. 6-203932). FIG. 7 is a cross-sectional view illustrating an important part of such a conventional relay connector.
As shown in FIG. 7, the connector has a housing 301 formed of an insulating material, and a plurality of terminals 302 held by the housing 301 which are formed of a conductive material. The terminals 302 are securely mounted, by press-fit, in terminal holding grooves formed in a cable insertion opening of the housing 301. Each of the terminals 302 has, on each of the upper and lower sides thereof, a cantilever-like arm member extending from a main body seated in an innermost portion of the housing 301 toward the front face of the housing 301.
A first flat cable 303 and a second flat cable 306, with their one ends disposed to be stacked one upon another, are inserted into the cable insertion opening of the housing 301. The first flat cable 303 is provided with a plurality of conductive leads 304 formed on one surface (the lower surface as viewed in FIG. 7) of a body formed of a strip-shaped insulating material, and an insulating layer 305 covering the surfaces of the conductive leads 304. The second flat cable 306 is provided with a plurality of conductive leads 307 formed on one surface (the upper surface as viewed in FIG. 7) of a body formed of a strip-shaped insulating material, and an insulating layer 308 covering the surfaces of the conductive leads 307. An electronic component 309 is mounted on the first flat cable 303, and terminals of the electronic component 309 are connected to the conductive leads 304.
The insulating layer 305 is partially removed at the end of the first flat cable 303 to expose the conductive leads 304 thereof, and the insulating layer 308 is partially removed for the same purpose at the end of the second flat cable 306. Therefore, as shown in FIG. 7, by stacking the two ends of the cables together and inserting them as a single piece into the cable insertion opening of the housing 301, the conductive leads 304 and 307 contact each other to establish an electrical connection to thereby connect together the first flat cable 303 to the second flat cable 306. The upper and lower arm members of the terminals 302 urge the first flat cable 303 and the second flat cable 306 from above and from below, and the conductive leads 304 and 307 are pressed against each other to ensure a connection between the first and second flat cables 303 and 306. A lock member (not shown) may be fit from behind the housing 301 in order that the upper and lower arm members of the terminals 302 are further pressed from above and from below by the lock member. This provides a sure connection between the two flat cables 303 and 306.
Nevertheless, in the above connector, a change in the electrical connecting resistance between the conductive leads 304, 307 might cause a change in the transmission characteristics of signals. That is, the conductive leads 304 and 307 are pressed together and connected to each other by the upper and lower arm members of the terminals 302. However, according to careful observation of the connection of both conductive leads 304 and 307, it is understood that, at a point corresponding to projected portions of the above-mentioned arm members contact of both conductive leads is ensured, but in a region lying in front of and behind the point, both may be alternately brought into contact with one another and separated apart from one another because of the uncertainty of contacting state. When the region of both conductive leads 304 and 307 that lie in front of and behind the point is in contacting state, the area of a portion in such a contacting state is rather large thereby decreasing the electric connecting resistance between the conductive leads 304 and 307. When the above-mentioned region in front of and behind the point is separated apart to lose contact, the area of the portion in the contacting state becomes narrow thereby increasing the electric connecting resistance between the conductive leads 304 and 307. Thus, the change in the electric connecting resistance between both conductive leads 304 and 307 could cause unstable transmission characteristics, resulting in becoming unable to stably transmit signals.